Where did the "east wind" borrowed by Kong Ming come from? There is actually a scientific basis behind it.

First of all, it is certain that Zhuge Liang did not borrow it. Lao Tzu said, "Heaven and earth are heartless, and everything is regarded as a grass dog. Heaven and earth have their own operating rules, and they will not take sides for a human war.

However, there is indeed this trend in history, but how did it come about? Looking through all kinds of materials, none of them can explain clearly. Most of them are just ambiguous answers such as "possible", "normal" and "not surprising", and none of them can give a clear statement. Some of them also involve a lot of technical terms such as "earth deflection" and "pressure gradient force", which are simply incomprehensible.

Let's try to explain it from a geographical perspective.

If you want to know where the east wind comes from, you must first understand how the wind is generated.

The authoritative explanation is that wind is a natural phenomenon caused by air flow and is caused by the difference of solar radiation.

Generally speaking, sunlight in different places will cause temperature difference, because there is temperature difference, the air will flow, so the wind will be generated. On the earth, this kind of atmospheric movement caused by the uneven surface temperature of the earth due to the difference of solar radiation is called atmospheric circulation. Atmospheric circulation has a fixed law, and the wind it produces is called trade wind.

As the name implies, trade winds are very trustworthy and come from the same direction all the year round. However, the geographical position of China is very special. We are located at the eastern end of Eurasia. The Qinghai-Tibet Plateau, the roof of the world, not only blocks the entry of trade winds, but is also surrounded by the Pacific Ocean, the largest water body in the world. So the wind that affects China is mainly monsoon.

Monsoon is a wind that changes with different seasons, which gives us an intuitive feeling that "blowing willow wind is not chilling" in spring and "the north wind rolls flowers" in winter. To put it simply, in this land of China, the northwest wind blows in winter and the southeast wind blows in summer. Spring and autumn are the times when two kinds of winds alternate. Because we like abbreviations, we often call northwest wind west wind or north wind and southeast wind east wind or south wind.

Let's not talk about the trade winds, but the monsoon related to China. So how is the monsoon formed?

There is a word in physics called specific heat. It is the heat absorbed or released by a substance with the same mass when the unit temperature rises or falls. It's a little roundabout. Let's make an analogy. Like a pot of water and oil, the specific heat of water is large. We burn a pot of water slowly and a pot of oil much faster. This is because their specific heats are different. Take the experience in our life as an example. In summer, if there is a big stone by the lake, it will become very hot, but the water in the lake is still very cold. This is because water has a large specific heat and absorbs the same heat, so the temperature of water will rise slowly and the temperature of stone will rise quickly.

By the same token, in the dead of winter, if you touch the stones by the lake again, you will feel very cold, and the water in the lake is still warm, so fish will not freeze to death if they swim in it. Among the substances we see every day, water has the largest specific heat, so under the same sunlight, the temperature of water rises the slowest. On the contrary, in the case of heat loss, the temperature of water drops the slowest. The same is true for drinking more water when you have a cold. Water can keep your body temperature relatively balanced.

We can compare Eurasia to that stone, and that lake is the Pacific Ocean. When summer comes, the northern hemisphere absorbs more heat than it emits, and the whole northern hemisphere begins to heat up. Eurasia has low specific heat because of sandstone soil structure, while the Pacific Ocean is full of water, with high specific heat and slow temperature rise.

Where the temperature rises rapidly, the air on the surface is heated, and the hot air rises due to the low density, forming a low pressure (you can imagine that the air above your head runs upward, is the pressure less? So it is called low pressure); In the Pacific, the situation is just the opposite. The air temperature near the water surface is lower than that near it, and the cold air sinks due to its high density, forming a high pressure. The air in the high-pressure area will inevitably go to the low-pressure area, so the warm and humid air flow in the Pacific Ocean will move to Eurasia, and then the southeast wind will be generated.

Similarly, in winter, the sun shines on the southern hemisphere, and the northern hemisphere loses more heat than it absorbs, and the temperature drops day by day. Or because of the large specific heat of water, the temperature in the Pacific Ocean drops slowly while the temperature in Eurasia drops rapidly when the same heat is lost. In other words, the air temperature in the Pacific Ocean is relatively high, and the hot air rises, forming a low pressure; However, the ground temperature in Eurasia is relatively low, and the cold air sinks, forming a high pressure. The air in the high-pressure area flows to the low-pressure area, thus producing a dry and cold northwest wind.

In the whole environment of China, the change of monsoon is caused by the revolution of the earth and will not be affected by any other conditions. Battle of Red Cliffs took place in the winter of 208 in the 13th year of Jian 'an. The earth revolves around the sun as it does today, and there is no change. So when the war broke out, the northwest wind was blowing in most parts of China. The place where Battle of Red Cliffs happened, that is, today's Hubei Province, belongs to the monsoon region, and there is no doubt that the northwest wind also blows.

Will there be special circumstances?

In fact, the generation of monsoon can be summarized in another sentence: it is caused by the difference of thermal properties between land and sea. But why not? Because this sentence is used to describe the land and sea breeze.

In fact, the principle of land-sea breeze is the same as that of monsoon, except that it does not change with the season, but with the day and night, and it occurs in some areas, mainly along the coast.

During the day, the sunshine at the seaside is strong, the land heats up quickly, and the seawater heats up slowly, so a low pressure is formed on the land, a high pressure is formed on the sea surface, and the air in the high pressure area moves to the low pressure area, forming a sea breeze.

At night, on the contrary, the land and sea began to radiate heat to the atmosphere, and the land cooled quickly and the sea surface cooled slowly, so high pressure formed on the land and low pressure formed on the sea surface, and the air in the high pressure area moved to the low pressure area, forming a land wind.

This is the principle of the formation of land-sea wind, which can form its own wind direction in local areas under the prevailing monsoon. Of course, the monsoon at this time should not be too strong, otherwise the land and sea breeze will not work.

There is no sea inland. If the sea is changed into a lake, this kind of wind will also be produced under the same conditions. For the sake of distinction, we call it lake-land wind.

So, is there a condition to produce lake and land wind near Chibi?

This is possible only if there is water first.

If you open the map near Chibi, you will find that there is only the Yangtze River near here, and the water area of the Yangtze River is very small and banded, which is not enough to affect the local climate, so we have to see if there are other waters or similar things.

If we go back in time, we really find that there used to be a large area of water here, that is Yunmengze.

First, make clear a concept: ancient rhyme and cloud dream.

In ancient times, from Hunan to Hubei, there was a Wang Yang. This is an ancient cloud and dream. Later, due to the sediment accumulation in the Yangtze River, Yunmengze was formed in the north of the Yangtze River, and Dongting Lake and its nearby plains were formed in the south of the Yangtze River. There is a difference between the north and the south because there is Hanshui River in the north, and the sediment carried by Hanshui River is also accumulated here, so there is no large water area like Dongting Lake in the north (Honghu Lake was formed only in the Ming and Qing Dynasties, and its volume cannot be compared with Dongting Lake), but a group of small lakes scattered like pearls.

Yunmengze is the general name of lakes in this area north of the Yangtze River. In other words, Yunmengze is a large and small lake with swamps and paths that people can hardly walk on. Although this geographical condition can't be compared with the ocean, it is no different from the great lakes because of its high water content.

During the Eastern Han Dynasty, Yun Mengze was still there. By the time we arrived in the Three Kingdoms, Yunmengze had just deposited, but it was unstable and the water area was still very large. In fact, when we look at the map of the Three Kingdoms period, we will find that the cities at that time were mainly built along the edge of Yunmengze, because there are still lakes and swamps everywhere, which are not suitable for human habitation. The later Jianghan Plain was formed after Yunmengze deposition.

Even today, the Jianghan Plain is still dotted with countless lakes, so it is conceivable that Yunmengze in the Three Kingdoms period still had a lot of water, which can be regarded as a big water body.

Solve the water problem, and then we'll find the mountain. Are there any mountains near Chibi?

Fortunately, no matter how human history changes, the changes in mountains are very small. In the southeast of Chibi, there is indeed a big mountain, that is, the Shogunate Mountain. Mufu Mountain is the boundary mountain between Hubei and Jiangxi today, and its volume is large enough to change the local climate in this area.

Well, we take Chibi as the center, Yunmengze in the northwest and Shogun Mountain in the southeast. As long as the conditions are met, the lake-land wind we mentioned earlier can be produced.

Suppose that it is sunny around Chibi on a winter day, and the Mufu Mountain has a small specific heat because it is a rocky mountain structure, and it heats up quickly after being irradiated by sunlight, forming a low pressure; Yunmengze has high water content, large specific heat and slow temperature rise, forming high pressure-the airflow in the high pressure area moves to the low pressure area, generating northwest wind, which is consistent with the monsoon wind direction at that time.

At night, because of the small specific heat, the temperature in the Shogun Mountain drops quickly, and the cold air sinks, forming a high pressure; The water in Yunmengze has been exposed to the sun during the day, and the temperature is already very high. At this time, the temperature drops slowly, and the hot air rises, forming a low pressure. At this time, the air flow in the high-pressure area moves to the low-pressure area, that is, the air flow in Mufu Mountain moves to Yunmengze, so the southeast wind is produced.

It can be concluded that when the monsoon activity is not strong, as long as the sunshine is good during the day, then at night, the southeast wind will be generated.

"Biography of the River Table" said: "The southeast wind is urgent." It can be seen that the southeast wind did blow that day, and the wind was quite strong. The "Jiangbiao" here refers to Jiangdong. We know that there is an idiom called "mountains and rivers on the outside", which means "inside and outside". The word "exterior and interior" is often used today, and exterior and interior are actually synonyms. Jiangbiao is just outside the river. Judging from the Central Plains regime, outside the Yangtze River is Jiangnan, which generally refers to Jiangdong in the lower reaches of the Yangtze River. Jiangdong was often called Jiangbiao during the Three Kingdoms period. In terms of latitude, Jianye is farther north than Jiangling and comparable to Xiangyang, but we seldom call the south of Jingzhou Jiangnan, because the core area of Jingzhou is in Jiangbei.

Anyway, why should we emphasize that it is sunny during the day? Why do you want to emphasize shogunate mountain?

Because the water temperature in Yunmengze will only be high when the sunshine is strong during the day, at night, the air pressure contrast with the land will be large, that is, the wind will be strong. Similarly, if there is no Mufu Mountain, as long as there is land, there will be a lake-land wind between it and Yunmengze, but the general land component is soil, which contains a certain amount of water, so its specific heat is not much different from that of the lake, while Mufu Mountain is a rock structure, and the stone does not contain water, so its specific heat is smaller, so the temperature drops faster, and the air pressure difference between it and Yunmengze is larger, resulting in stronger wind.

There is no record in history whether Battle of Red Cliffs occurs at night or during the day, but according to our analysis above, the northwest wind still occurs during the day, and the southeast wind only occurs at night. This is clearly stated in the Romance of the Three Kingdoms: There was no wind in the evening, and Zhou Yu was anxious, blaming Zhuge Liang for talking big, and the southeast wind didn't get up until midnight. The third night is midnight, which is twelve o'clock at night. This is very consistent with our speculation. When the sun just went down, the temperature on the Shogun Mountain had not dropped, and it was not until late at night that the temperature on the Shogun Mountain was low enough to produce lake wind and land wind.

In fact, it was because of Yun Mengze that Cao Cao was embarrassed when Huarong Road fell. Cao Cao fled from Wulin to Huarong through Yunmengze. Although there is a road in Yunmengze, there are swamps and muddy everywhere, which is very difficult to walk. In this escape, many old and weak soldiers filled the mud pit.

One more question. Sun Liulian's method of burning Chibi defeated Cao Jun, not on a whim, but after careful preparation. So how did they know there would be a southeast wind?

This is actually not difficult to understand. Zhuge Liang said that a general should know astronomy above and geography below, but the ancient people in China had limited knowledge of geography and meteorology. Today, we often rely on satellite cloud images to predict the weather and make inaccurate judgments, not to mention at that time! But don't forget, China is a farming nation, and farming depends on the weather, so it is very important to record the weather. Officials here will certainly make detailed records of the local climate. As time went on, they also found that the southeast wind occasionally blew here in winter.

It is under this premise that the allied forces of Sun and Liu decided to attack by fire. But when the southeast wind will blow, no matter how detailed the historical records are, it is impossible to predict what will happen in the future, so they wait while preparing, and when everything is ready, they just need the east wind, so they wait for the southeast wind to borrow the wind in the middle of the night, and the wind will help the fire, burning Cao Jun to flee. History has also changed because of this fire.

After Battle of Red Cliffs, Cao Cao suffered heavy losses and hastily retreated to Jiangling. Sun and Liu went hand in hand and pursued them all the way. Cao Cao was worried about the instability in the rear, so he left Coss and Huang Xu in Nanjun (the place where Jiangling was ruled), Wen Pin in Jiangxia (the part in the north of the Yangtze River), Le Jin in Xiangyang and himself in the north.

Cao Cao probably didn't expect that he would never have a chance to come to Jingzhou after this trip.